Thyroid storm Treatment

Pharmacotherapy

The main aims of medical therapy are as follows-

1. Reduce effects of thyroid hormone on peripheral tissues.
2. Decrease further synthesis of thyroid hormone
3. Decrease release of hormone
4. Prevent further TH secretion and peripheral conversion of T4 to T3.

The medications used to accomplish the above aims are described as follows (in order of the aims)-

1) Beta-blockers

Beta blockers block peripheral conversion of T4 to T3. Exercise caution while using in patients with congestive heart failure and cardiomyopathy. They are known to precipitate cardiac arrest in patients with cardiomyopathy.

1. Propanolol- nonselective beta adrenergic antagonist, used widely.
2. Esmolol- beta 1 specific antagonist with a short duration of action.

2) Antithyroids

Propylthiouracil is the drug of choice for thyroid storm that prevents organification, trapping of iodide to iodine and also peripheral conversion of T4 to T3. It is available only as per oral medication and hence comatosed patients may need to be given via nasogastric tube. It causes more rapid decrease in T3 levels than methimazole.

Methimazole has similar mechanism of action as propylthiouracil except it does not inhibit peripheral conversion. It is more potent than propylthiouracil. It is also only available as per oral formulation. It has longer duration of action, used in non life threatening situations. It is less hepatotoxic therefore all patients started on propylthiouracil should be started on methimazole before discharge.

Few patients may be one unable to take antithyroids due to side effects like agranulocytosis, hepatotoxicity and/or allergy. Thyroid storm has been found to develop in patients upon discontinuation of antithyroids. In that case, on should go for a week course of steroid, Lugols iodine, beta blockers and proceed with thyroidectomy on the 8th day.

3) Iodides

Lugol solution has 100 mg potassium iodide and 50 mg iodine. It also inhibits peripheral conversion of T4 to T3 within hours. It has to be given in thyroid storm but atleast 1 hour after antithyroid administration. This is done so that there is no chance that iodine be used to make new thyroid hormones. By giving antithyroids first all synthesis steps will be blocked and iodine then would be an added bonus in blocking release of already formed hormones. Side effects of iodine are direct injury to esophagus.

4) Glucocorticoids and iodine contrast agents

The 4th aim is fulfilled by both glucocorticoids and iodine contrast agents.

• Steroids have been found to be associated with improved survival. They also effect the autoimmune process in case of crisis due to Graves disease. Preferred steroid is hydrocortisone.

• Iodinated contrast agents are presently not available in the US due to doubts on their efficacy. As was with iodine, these are also given an hour after antithyroids.

Other therapies

• Lithium- given to block release of thyroid hormone but its toxic to liver.

• Plasmaphereis- has been tried when other therapies failed.